Shadow-line projector for assembly reference

ABSTRACT

A shadow-line projector adapted to establish reference lines on a work surface, the lines being shadows cast by stripes located on a transparent sheet preferably carried by rollers capable of shifting the sheet to project a plurality of sets of reference lines in sequence.

United States atent 11 1 Carter et al.

14 1 July 31, 1973 [54] SHADOW-LINE PROJECTOR FOR 1,953,299 4/1934 Grant 353/42 X ASSEMBLY REFERENCE 2,506,610 5/1950 Mueller.. 143/168 B x 3,323,415 6/1967 Toblas 353/28 X [75] Inventors: Andrew G. Carter; Charles L. 745,424 1/1903 Davis.. 240/2 D X Morgan, both of Grand Rapids, 3,563,144 2/1971 Fukino 352/227 X Mich.

[73] Assignee: Carter Prorlucts company, lnc., primary Examiner Richard Queisser Grand Assistant Examiner-Daniel M. Yasich 22 Filed: Dec. 10, 1970 ArwmeyGlenn Morse [21] Appl. No.: 96,871

[57] ABSTRACT [52] US. Cl. 353/62, 143/168 B, 240/2 D [51 Int. Cl. G031) 21/00 A Shad0w |ine projector adapted to establish reference [58] Fleld of Search 240/2 D; 143/168 B; lines on a work Surface, the li being Shadows cast by 353/42 122; 352/227, 62 stripes located on a transparent sheet preferably carried by rollers capable of shifting the sheet to project References Cited a plurality of sets of reference lines in sequence.

UNITED STATES PATENTS 2,696,753 12/1954 Sega] et a1. 353/122 X 3 Claims, 17 Drawing Figures PATENTEB L I913 3. 749 .485

sum 1 [1F 6 INVENTORS Fig. 3 Andrew 6. Carter Charles L. Morgan A rromvzy v PATENIEU 1 3. 749.485

sum u BF 6 nvvmvroms Andrew 6. Carter Charles L. Morgan ATTORNEY PATENIED JUL 3 SHEET 5 BF 6 I o L I Fig. 14

5 Y M 0 ME TF0 N eg R En Wm yam T N A L w mu d0 nh AC Y B w m SHADOW-LINE PROJECTOR FOR ASSEMBLY REFERENCE BACKGROUND OF THE INVENTION Shadow-line projectors have been used to establish reference lines on work surfaces in a number of situations. The applications of the shadow-line principle in general use are used to indicate the path of a cutting or machining operation on stock being fed into a machine. A typical example of such an application is shown and described in our application Ser. No. 79,207, filed on Oct. 8, 1970. The device illustrated in this application indicates the path of cut that a saw will follow on a rough plank being moved into the saw on a feed table.

The present inventors have recognized that it would be desirable to utilize the principles of shadow-line projectors in establishing reference lines to assist workmen in assembling a number of components in particular dimensional relationships with each other. In the manufacture of prefabricated housing, for example, it is necessary to put together a considerable number of panel sections, each of which includes an assortment of parallel studs and interconnecting members, and additionally requires the placement of a number of items in particular positions in the wall structure. Known forms of shadow-line devices are not practical for this sort of assembly operation, primarily because of the difficulty in re-aligning the interference lines that produce the shadows. A given floor area is not usually devoted exclusively to the assembly of one particular wall section. Since a housing unit will contain a number of these wall sections which are not identical in construction, it would be necessary to re-align the shadow-line device each time the unit assembled was changed. This would be a time-consuming operation, and would require considerable care of the part of the workmen responsible for the readjustment. The general objective of the present invention has been to utilize the principles of shadow-line projection in a device capable of projecting a large number of reference lines, in which the shifting from one pattern of lines to another is predetermined in the sense that an entire pattern is shifted at once.

SUMMARY OF THE INVENTION A projector embodying the present invention provides a series of stripes on a transparent sheet, the strips being opaque and of a desired width to project a particular width of shadow on a work surface. A section of this transparent sheet corresponds to a particular assembly project, and all of the parallel reference lines required for this project are incorporated on that section of the sheet. Preferably, the sheet is carried by rllers engaging the opposite ends of the sheet in the manner of a scroll. The section of the sheet being exposed to the projection is supported by a transparent panel, which preferably includes transparent stiffening beams to maintain the sheet in a co-planar relationship. A pressure plate on top of the sheet, sandwiching the sheet between the support panel and the pressure plate, assists in maintaining the flatness of the sheet so that the projection is a distortion-free as possible. It is obvious that any wave-like deformity of the sheet carrying the interference stripes will induce similar deformity in the shadow-line. It is also referable that the materials, selected for the sheet, the support panel, and the pressure plate be selected so that electrostatic attraction can be used to assist in maintaining the flatness of the sheet, both through direct adhesion, and by establishing sufficient drag to the movement of the sheet to tend to eleminate any accumulation of wrinkles. The preferred form of the invention also includes perforations in both the supporting panel and the pressure plate to eliminate the formation of bubbles of air that will tend to interfere with flatness. The entire unit providing the support for the sheet is mounted in a frame preferably suspended from a conventional linear light source in which light is generated by an incandescent straightline filament. The stripes on the transparent sheet are arranged parallel to this filament. Transverse reference lines are either established by rotating the projector about a vertical axis (accompanied by a suitable shifting of the section of the transparent sheet to present the new set of reference-lines), or by the use of a second projector adapted to project lines on the same working surface. The shifting of the section of the transparent sheet is accomplished preferably by a motor drive capable of shifting the scroll in either direction.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a complete shadowline projector embodying the present invention.

FIG. 2 is an end elevation of the lower portion of the device shown in FIG. 1, and containing the structure for the placement and support of the sheet carrying the interference stripes. FIG. 2 is on an enlarged scale over FIG. 1.

FIG. 3 is a section on the plane 3--of FIG. 4.

FIG. 4 is a plan view of the portion of the machine shown in FIG. 2.

FIG. 5 is a view of the opposite end of the structure from that shown in FIG. 2, on a reduced scale.

FIG. 6 is a section on the plane 6-6 of FIG. 4.

FIG. 7 is a section on the plane 7-7 of FIG. 4.

FIG. 8 is a schematic wiring diagram showing the circuit for controlling the motors used to position the rollers.

FIG. 9 is an exploded view showing the components of the assembly illustrated in FIG. 1.

FIG. 10 is a perspective view showing the placement of the interference strips on the transparent sheet.

FIG. 11 illustrates a folded form of the structure shown in FIG. 2. I

FIG. 12 illustrates a modified form of suspension link for interconnecting the unit shown in FIG. 2 with the light source.

FIG. 13 illustrates the opposite link used in association with the FIG. 12 link.

FIG. 14 illustrates the folded position of a device incorporating the FIG. 12 and FIG. 13 suspension links.

FIG. 15 is an enlarged view of the support unit for the transparent sheet.

FIG. 16 is a perspective view of a perforated pressure plate used on top of the transparent sheet.

FIG. 17 illustrates a modified support assembly for the transparent sheet, utilizing perforated surfaces.

DESCRIPTION OF THE PREFERRED EMBODIMENT The components of the projector shown in FIG. 1 are best shown in FIG. 9. The conventional linear light source 20 contains a normally incandescent straight line filament running generally in a direction parallel to the longest dimension of the device. Light is projected downwardly through the open bottom of this device,

and through the transparent components of the shadow-line unit. A frame generally indicated at 23 is suspended from the light source by the links 24 and 25 pivotally connected to the frame 23 as indicated at 26-27 and 28-29. A rectangular piece 30 is normally provided to reinforce the lower flange of the projector housing, and provide a firm shelf extending from the ends of the housing for supporting the bail-shapped link members 24 and 25.

The frame 23 is essentially a box-like structure of sheet metal having an open bottom defined by the marginal flange 31. Rollers 32 and 33 are rotatably mounted on opposite sides of the frame structure 23, as best shown in FIGS. 3, 4, 6 and 7 These rollers are of a type of structure commonly associated with roller curtains, and include a central cylindrical member 34 having a shoulder pin 35 functioning as a bearing at one end, and having a coupling 36 at the opposite end for interconnecting the roller with its drive motor 37. This construction is typical of two roller assemblies, the drive motors being protected by the housings 38 and 39. A flexibleconduit 40 extends between these housings for carrying the wiring associated with the schematic housings for carrying the wiring associated with the schematic circuit diagram shown in FIG. 8. Energy is supplied to the circuit via the plug-in connector 41, and applied to the motors 37a and 37b through the leads 42 and 43. The ground connection 44 is preferable. The direction of rotation of the motors 37a and 37b is controlled by the toggle switch 45, through manipulating the lever 46 between the positions indicated in dotted lines in FIG. 8. This circuit is a conventional arrangement, and the effect of it is to apply the voltage selectively to either the motor 37a or the motor 37b. As either one of these motors is activated, the roll associated with the opposite motor drags as an idler. Each of the motors isof a conventional type of construction incorporating a clutch device which connects the motor to the output shaft only when power is applied.

The reference shadow-lines are generated by intercepting the light from the light source 20 with the interference lines established by the stripes 49, shown in FIG. 10, applied to the sheet wound upon the rollers 32 and 33. It is usually most convenient to apply the stripes 49 in the form of narrow pressure-sensitive tape which can be semi-permanently attached to the sheet 50. This sheet is, of course, transparent, and is preferably of a clear acetate.-

The structure for supporting the transparent sYeet 50 includes the transparent supporting panel 51 stiffened by the transparent beams 52 and 53. These beams are preferably adhesively secured to the underside of the panel 51, and rest on the transparent lower panel 54. It is preferable that the beams 52 and 53 also be adhesively secured to the lower panel. The adhesive used on the upper and lower edges of the beams 52 and 53 must also be transparent to avoid casting a transverse shadow. The lower panel 54 rests on th flange 31 of the frame 23, and is secured to the flange by fastenings indicated at 55 and 56 in FIG. 7. The subassembly including the panel 51, the beams 52 and S3, and the lower panel 54, is additionally supported by the shelves formed by the angles 57 and 58 secured to the sides of the box frame 23 in any convenient manner. These shelves engage the underside of the panel 51. This structure forms a transparent table over which the sheet 50 is selectively placed by the motors 37a and 37b. The formation of at least the panel 51 of plexiglass has been found to provide the necessary transparency and also developed the electrostatic attraction between the panel surface and the sheet 50 to assist in maintaining the flatness of the sheet to avoid distortion of the shadow-lines. This arrangement has been found very effective in the construction of a machine in which the panel 51 was on the order of 4 feet long by 2 feet wide. Adequate transparency resulted from the use of plexiglass of a quarter inch thickness for the panel 51 and the beams 52 and S3, and one-eighth of an inch in thickness for the lower panel 54. A further and preferred) expedient for assuring the flatness of the sheet 50 is the transparent pressure plate 59. This plate may either rest freely on the top of the Sheet 50, being confined against lateral movement by the sidewalls of the box frame 23, or may be hinged to the box structure as shown at 60. This plate is also preferably of one-eighth of an inch thick plexiglass. In the modification of the invention shown in FIGS. 16 and 17, the pressure plate 61 and the support panel 62 are preforated to permit the escape of air, and thus inhibit the development of an air cushion between the sheet 50 and the support structure. The sub-assembly shown in FIG. 17 includes the same lower plate 54 and beams 52 and 53 as in the non-Perforated sub-assembly shown in FIG. 9. In both cases, the opposite edges of the support panel are rounded as shown at 63-64 in FIG. 17 and 65-66 in FIG. 9, to provide a gentle curvature at the points where the sheet 50 passes over these edges toward Jhe respective rollers.

When the device is packed for shipment, or is stored during periods of non-use, the suspension links 24 and 25 are disconnected from the light source 20, and fold downwardly against the box frame 23 as shown in FIG. 11. This folding action can be improved at a relatively small increase in cost by the formation of one of the suspension links with an off-set as shown at 67 in FIG. 12. This off-set permits the suspension link 68 to fold down in to parallism with the opposite link 69, which is formed without an offset, but is capable of folding below a plane defined by the top edge of the box structure 23.

We claim:

1. In a shadow line projector, having a linear light source, a frame connected to said light source, and shadow generating means mounted on said frame to intercept light from said source and generate a shadow, an improved shadow-generating means comprising;

a transparent sheet having successive groups of interrelated opaque stripes disposed parallel to said linear light source;

a pair of rollers parallel to said linear light source mounted, respectively, on opposite sides of the frame and connected, respectively, to opposite ends of said sheet;

I a transparent panel carried by said frame in supporting contact with the portion of said sheetextending between said rollers;

at least one transparent stiffener beam affixed to said panel on the face thereof opposite that which supports eaid sheet; and

a transparent flattening plate carried by said frame and on the opposite side of said portion of said sheet from said panel.

2. A Projector as defined in claim 1, wherein at least one of said panel andplate are perforated.

3. A projector as defined in claim 1, wherein said sheet is of a material selected to normally exhibit electrostatic attraction to at least one of said panel and said plate.

at a a a m 

1. In a shadow line projector, having a linear light source, a frame connected to said light source, and shadow generating means mounted on said frame to intercept light from said source and generate a shadow, an improved shadow-generating means comprising; a transparent sheet having successive groups of interrelated opaque stripes disposed parallel to said linear light source; a pair of rollers parallel to said linear light source mounted, respectively, on opposite sides of the frame and connected, respectively, to opposite ends of said sheet; a transparent panel carried by said frame in supporting contact with the portion of said sheet extending between said rollers; at least one transparent stiffener beam affixed to said panel on the face thereof opposite that which supports eaid sheet; and a transparent flattening plate carried by said frame and on the opposite side of said portion of said sheet from said panel.
 2. A Projector as defined in claim 1, wherein at least one of said panel andplate are perforated.
 3. A projector as defined in claim 1, wherein said sheet is of a material selected to normally exhibit electrostatic attraction to at least one of said panel and said plate. 